As a useful catalyst to be used for such a hydrogenation reaction, a copper/chromium oxide catalyst has been widely known as a copper chromite catalyst (e.g. Non-Patent Document 1).
As a specific example, a process for producing aniline has been known wherein a gaseous nitrobenzene is reduced with hydrogen by means of a copper/chromium oxide catalyst under such conditions that the reaction temperature is from 180 to 370° C., the pressure is from 0.1 to 0.5 MPa and a nitrobenzene concentration is from 2 to 14 vol % (e.g. Patent Document 1). However, such a catalyst containing chromium oxide is likely to cause environmental contamination or health hazard, and a due care is required in its handling, and further, substantial labor and costs have been required also for the treatment and recovery of the catalyst used.
Further, a process for producing an aromatic amine by hydrogenation of an aromatic nitro compound by using a modified Raney copper which comprises copper, iron and aluminum as basic components, has been proposed (e.g. Patent Document 2). However, a Raney metal catalyst is usually susceptible to deterioration of the activity due to surface oxidation and is therefore required to be stored in water or in an inert gas atmosphere, and a due care is required for its handling. Further, while its activity is high, it has such a problem that the durability is inadequate.
Recently, a molded hydrogenation catalyst has been proposed which is made of a natural clay mineral such as copper, calcium silicate, attapulgite, etc. (e.g. Patent Document 3). While such a molded catalyst is excellent in strength and durability, it contains natural material as raw material, and it has a drawback that reproducibility is poor with respect to the composition or particle size of the catalyst to be produced, due to variations in its composition or physical properties.
Further, a molded catalyst comprising copper, calcium silicate, hydrotalcite, etc., has been proposed (e.g. Patent Document 4). However, such a molded catalyst employs hydrotalcite having the composition controlled, and petal-shaped calcium silicate, and therefore, it has an economical problem that the price is obliged to be relatively high.